Retroreflector display system for generating floating image effects

ABSTRACT

A display system is provided that combines the use of a display element with a beamsplitter and at least one retroreflector to provide an image (2D or 3D depending upon the output image from the display element) that appears to be floating in space some distance from the beamsplitter. For example, light that is bounced off/reflected and/or that is transmitted through the beamsplitter may be reflected from the reflective surface of the retroreflector toward the beamsplitter. The beamsplitter directs this light, through reflection or transmission, into a viewing space such that the 2D or 3D image can be viewed by a viewer as it appears to float a distance from the nearest surface of the beamsplitter and, typically, some distance above the ground/floor upon which viewers are walking. The floating image may be relatively bright so that it is viewable in low and brighter light conditions.

BACKGROUND 1. Field of the Description

The present description relates, in general, to displays adapted toprovide the illusion that a virtual or projected image is athree-dimensional (3D) image or has volume or a two-dimensional (2D) or3D image is floating in space like a hologram from a futuristic movie.More particularly, the description relates to systems and methods forproducing 2D or 3D images that appear to float in space using one ormore retroreflectors or sheets of retroreflective material (also calledretroreflective elements/devices, retro reflective material/sheets, andretro-reflective material/sheets within the industry).

2. Relevant Background

Today, there is a growing demand for displays with exciting andeye-catching visual effects. For example, there is a growing trendtoward using 3D projection techniques in theatres and amusement parksand in home entertainment systems including video games andcomputer-based displays. In many conventional 3D projection techniques,the right eye and the left eye images are delivered separately todisplay the same scene or images from separate perspectives so that aviewer sees a three dimensional composite, e.g., certain characters orobjects appear nearer than the screen and other appear farther away thanthe screen. However, stereoscopy, stereoscopic imaging, 3D imaging, and3D or volumetric displays are labels for any technique capable ofcreating the illusion of depth in an image.

Often, the illusion of depth in a photograph, movie, or othertwo-dimensional image is created by presenting a slightly differentimage to each eye or the creation of parallax. In most animated 3Dprojection systems, depth perception in the brain is achieved byproviding two different images to the viewer's eyes representing twoperspectives of the same object with a minor deviation similar to theperspectives that both eyes naturally receive in binocular vision.

There is a continuous desire and need to provide new techniques thatprovide cost effective but eye-catching content with depth anddimension. For example, it is desirable to grab the attention of crowdsin shopping malls, on busy streets, in amusement parks, and othercrowded facilities such as airports and entertainment arenas. Asdiscussed above, 3D imagery and volumetric displays are exciting ways toappeal to viewers and hold their attention. However, the use of 3Dimagery has, in the past, been limited by a number of issues. Typically,3D projection technologies require the viewer to wear special viewingglasses. This is often inconvenient for many applications and cansignificantly add to costs to provide the 3D media for projection andalso for the special eyewear that has to be provided to the viewer.

Some attempts have been made in providing volumetric displays withoutthe need for eyewear, but each has its own limitations. For example,displays providing a scrim projection or traditional Pepper's Ghostillusion are common tools used throughout amusement parks and othersettings. These displays allow placement of a virtual character orobject (i.e., a ghost, a video of a character, or the like) within areal world scene. A scrim projection is usually accomplished by using aprojection onto a scrim (e.g., an open weave material appearingtransparent when lit from behind but providing a projection surface whenlit from the front or viewer's side) while a Pepper's Ghost is areflection of a display in a beam splitter. Unlike directly viewing anopaque monitor, the scrim and the beam splitter are partiallytransparent to the viewer (even when lit from the front) so thedisplayed character is not framed by the display. The virtual charactercan be placed relatively seamlessly behind real world objects or props(foreground elements) and in front of real world objects or props(background surfaces and elements). Unfortunately, the partialtransparency of the scrim or the beam splitter also leads to the virtualcharacter having low contrast and being semi-transparent, and the imagesproduced are often relatively small in size.

Hence, there remains a need for a display system that is adapted toproduce 2D and/or 3D images (without the need for viewers to wearspecial eyewear) that appear to float in that it is not projected upon aprojection screen or other surface. For example, the floating image maybe in a space in which viewers may be present such that the viewers canbe near to the image and can, in some cases, walk about and interactwith the floating image. Preferably, the display system would beconfigured to produce a floating image that can be large in scale and,in many applications, be visible to the viewer not only in dark rooms orspaces but also in more highly illuminated rooms or spaces (e.g., a 3Dimage may float in an outside space near a queue for a ride orattraction at an amusement or theme park or in a lobby of a movietheater).

SUMMARY

To address the above problems and ongoing needs, a display system isprovided that combines the use of a display element with a beamsplitterand at least one retroreflector to provide an image (2D or 3D dependingupon the output image from the display element) that appears to befloating in space some distance from the beamsplitter. For example,light that is bounced off/reflected and/or that is transmitted throughthe beamsplitter may be reflected from the reflective surface of theretroreflector toward the beamsplitter. The beamsplitter directs thislight (through reflection and/or transmission) into a viewing space suchthat the 2D or 3D image can be viewed by a viewer as it appears to floata distance from the nearest surface of the beamsplitter (and, typically,some distance above the ground/floor upon which viewers are walking).

The floating image can be produced to be relatively bright so that it isviewable in low and brighter light conditions. The display system isalso advantageous as it is solid state with no moving parts and becauseit is easy to implement and scale from a smaller image to a relativelylarge one (e.g., from a floating image with a height of several inchesto several, or even, many feet). The cost to implement the displaysystem is also relatively low, and it can be packaged in a relativelysmall space with easy access for engineering and maintenance.

More particularly, an apparatus or display system is provided that isadapted for generating floating images. The apparatus includes a displayelement displaying an image with first light from a display surface.Significantly, the apparatus also includes a retroreflector with areflective surface facing the display surface, with the reflectivesurface being formed with or of a retroreflective material. Theapparatus further includes a beamsplitter disposed between the displayelement and the retroreflector with a first surface facing the displaysurface to receive the first light. During operations of the apparatus,the beamsplitter transmits a portion of the received first light assecond light toward the reflective surface of the retroreflector, thereflective surface reflects the second light as third light toward asecond surface of the beamsplitter that is opposite the first surface,and the beamsplitter reflects a portion of the third light as fourthlight into a display space to provide a displayed image at a distancefrom the second surface of the beamsplitter.

In exemplary embodiments, the reflective surface and the display surfaceare planar surfaces, with the reflective surface being parallel to thedisplay surface. The first surface of the beamsplitter typically isoriented to extend at a non-zero angle relative to the display surface(e.g., to not be parallel such as at a 45 degree angle). The displayedimage is a real image provided at a convergence or display plane locateda distance from the second surface of the beamsplitter that matches theseparation between the beamsplitter and the display element. In somepreferred embodiments, the display element comprises a monitor with anoutput luminence of at least 2500 Nits. For example, the display elementmay take the form of a liquid crystal display (LCD) monitor. In otherembodiments, though, the display element is a monitor or multi-leveldisplay assembly, and the image from the display element is athree-dimensional (3D) image.

The apparatus may further include a second retroreflector positionedwith a reflective surface including retroreflective material facing thefirst surface of the beamsplitter and oriented to be orthogonal to thereflective surface of the retroreflector. In such embodiments, theapparatus may also include a lens element (such as a sheet oftransparent material with an array of microlenses on a surface facingthe beamsplitter) disposed between the reflective surface of the secondretroreflector and the first surface of the beamsplitter, and the lenselement can be positioned a distance from the reflective surface of thesecond retroreflector that is equal to a focal distance of one or morelenses of the lens element.

Still further, the apparatus may include a scrim positioned between thesecond surface of the beamsplitter and the display space. The apparatusmay also include a prop or object in the display space with a surfacebelow, above, or to the side of the displayed image. In suchimplementations, at least a portion of the surface of the prop islocated at a separation distance from the second surface of thebeamsplitter that equals the distance between the displayed image andthe second surface of the beamsplitter.

In some single retroreflector embodiments, the first light from thedisplay element has a first polarization. The beamsplitter may bepolarized to be transmissive to light having the first polarization andto block or reflect light with other polarizations (e.g., to lighthaving a polarization differing from the first polarization). Theapparatus may further include a waveplate (e.g., a quarter waveplate)between the second surface of the beamsplitter and the reflectivesurface of the retroreflector. During apparatus operations, the secondlight may have a second polarization and the third light may have athird polarization after passing through the waveplate such that thethird polarization differs from the first polarization as is reflected.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side, schematic view of a display environment or space inwhich a display system or apparatus of the present description isoperating to display a floating 3D image to two (or more) viewers (whodo not need to wear special eyewear);

FIG. 2 is a side, schematic view of a display environment similar tothat shown in FIG. 1 but including another example of a display systemor apparatus of the present description;

FIG. 3 is a side, schematic view or function block diagram of anotherembodiment of a display system or apparatus utilizing polarized lightand a single retroreflector to provide a floating displayed image to aviewer;

FIG. 4 is a side, schematic view or functional block diagram similar tothat of FIG. 1 showing modification of the display system or apparatusto include interactive features and/or functionality;

FIG. 5 is a side, schematic view or functional block diagram similar toFIG. 1 showing modification of the display system to include a microlens element (e.g., a sheet or array) to enhance clarity of thedisplayed image;

FIG. 6 illustrates a side perspective view of a retroreflective sheetpaired with a sharpening or focusing element for use in any of thedisplay systems of FIGS. 1-5;

FIG. 7. Illustrates a retroreflective sheet paired with anotherembodiment of a sharpening or focusing element including convex lensesof differing sizes arranged in a random pattern (relative to the arrayof FIG. 6);

FIG. 8 illustrates a retroreflective sheet paired with anothersharpening or focusing element that includes a plurality or array oflenticular lenses (or lenticules);

FIG. 9 illustrates a sharpening element disposed between a beamsplitterand a retroreflector, with the sharpening element making use of aplurality of elongated slits in an opaque (or less transparent)substrate;

FIG. 10 illustrates a sharpening element similar to that of FIG. 9 butwith horizontal slits providing vertical sharpening rather thanhorizontal sharpening;

FIG. 11 illustrates an embodiment of a sharpening or focusing elementpaired with a retroreflective surface that makes use of a spatial lightmodulator to provide arrays of slits or pin-holes to provide anaddressable and changeable sharpening of the retroreflection;

FIG. 12 illustrates another focusing element that provides preferentialsharpening of polarized light when paired with a polarized light sourceand a retroreflective surface;

FIG. 13 illustrates yet another sharpening or focusing element that canbe used with retroreflective sheet to provide color-selectivesharpening;

FIG. 14 illustrates use of a translation assembly to provide thefocusing element translational motion to disguise or hide the presenceof the focusing element to viewers;

FIG. 15 illustrates a focusing element for use in sharpening or focusingretroreflection using liquid lenses;

FIG. 16 illustrates a display system that uses two lenses along with tworetroreflectors to provide a floating image;

FIG. 17 illustrates a display system embodiment utilizing a polarizeddisplay along with a pair of retroreflectors to provide a floating realimage in a display or viewing space;

FIGS. 18A-18D illustrate another display system embodiment utilizing apolarized display and a retroreflector to generate a floating real imagein a display or viewing space; and

FIGS. 19A-19D illustrate another display system embodiment that issimilar to the system of FIGS. 18A-18D but with an inline arrangementinstead of using a 90-degree bend.

DETAILED DESCRIPTION

Briefly, a display system is described that is specially configured toproduce a clear and relatively large (or scalable from small to largesizes of inches to several or many feet) floating image. The floatingimage may be 2D or 3D and may be presented in still or video format inspace or near to a display pedestal or a prop provided in the viewingarea. Examples of uses of such floating images or hologram-like effectsinclude a floating talking head, a floating control panel, moving 2D or3D stream of light extending from a futuristic weapon, and so on. Theviewer may be able to walk near to and even around, in some cases, thedisplayed image, and some embodiments provide the viewer withinteraction options that can cause the image to change based on theinteraction data (e.g., did the user select an item on a control panel,did the user “move” a 3D game piece relative to a pedestal game or propgame surface, and the like).

Prior to turning to the supporting figures and exemplary implementationsof display systems, it may be useful to first discuss a display systemdiscovered by the inventors as part of prototyping a display to providea floating image concurrently viewable by a plurality of viewers in aview space without the need for special eyewear. The prototyped displaysystem included a large beamsplitter (e.g., a square or rectangularplastic or glass beamsplitter that was 150 centimeters on a side). Asimilarly large (e.g., somewhat smaller in dimensions than thebeamsplitter) display element was provided in the form of a liquidcrystal display (LCD) television (TV), and the display element wasoperated to display 2D and 3D images. The longitudinal axes of thebeamsplitter and the display element were parallel, but the surface ofthe beamsplitter proximate to and facing the display element was at anangle (45 degrees, for example) to the display element's front surface.

The display element was positioned above the beamsplitter (e.g., withthe display element's front or display surface parallel to the floor orviewing space platform), but other prototypes were envisioned in whichthe beamsplitter and display element would be vertically oriented withthe display element off to the side of the beamsplitter (e.g., with anarrangement similar to many conventional Pepper's Ghost displays). Thelight associated with these displayed images was directed from thedisplay element's front surface (e.g., a monitor screen) toward thebeamsplitter where a fraction is passed (e.g., the beamsplitter istransmissive to the light but about 50 percent of the brightness is lostat each splitting) on to a reflective element or reflector.

The reflective element was positioned directly below and with itsreflective surface facing and parallel to the display element's front ordisplay surface. Significantly, the reflective element took the form ofa retroreflector or sheet of retroreflective material with itsreflective surface facing the beamsplitter and display element. Thelight that was passed through the beamsplitter is reflected back towardsthe beamsplitter with a minimum of scattering. A fraction (e.g., 50percent) of the light from the retroreflector is reflected off thebeamsplitter's lower surface (or second surface facing theretroreflector) and out into a viewing space to provide a displayed orfloating image. The displayed/floating image is at a distance thatmatches the distance from the beamsplitter and the display element'sdisplay/front surface and is a real image. The displayed or floatingimage was perceived or viewed differently by the left and right eye ofthe viewer (who was not wearing special eyewear), and appears to befloating due to the use of the beamsplitter rather than originating at adisplay device's surface.

In the prototype, context for this floating image was provided to theviewer by positioning a pedestal or other prop below the floating ordisplayed image such that it appeared to float directly above the topsurface of this pedestal/prop. A light source was provided on the top ofthe pedestal so that this light source appeared to be the source of thedisplayed, floating image (e.g., a hologram effect was produced by theprototyped display system). A scrim was also placed in front of theassembly between the viewer and the beamsplitter to allow a largepercentage of the light from the beamsplitter to reach the viewing areaand the display plane/focal plane but to disguise the source (e.g., toprovide the appearance of an opaque wall.

The distance between the beamsplitter and the front surface of thedisplay element defines how far from the lower or second surface of thebeamsplitter and a scrim (the disguising wall) the image will bedisplayed in the viewing space. In one prototype the distance from thecenter of the display element's surface to about the center of the topor first surface of the beamsplitter was in the range of 5 to 10 feetsuch that the image appeared to float a relatively large distance off ofor in front of the scrim/disguising wall (e.g., about 7 feet).

FIG. 1 is a side, schematic view of a display environment or space 100in which a display system or apparatus 110 of the present description isoperating to display a floating 3D image 140 to two (or more) viewers104, 106 (who do not need to wear special eyewear). The first viewer 104may be relatively close (e.g., d₁ is 0 to several feet) to the displayedfloating image 140, which is displayed relative to a focal or displayplane (or plane of convergence as the image 140 is a real image) 141,while the second viewer 106 may be relatively far away (e.g., d2 is 5 to30 feet or more). The light traveling to or viewed by the viewers 104,106 is shown by arrows 105 and 107, respectively (or these arrows 105and 107 may be considered as defining the viewing angle of the viewers104 and 106).

The floating image 140 is shown to be displayed over a top surface 152of a prop in the form of a pedestal or table 150, with a width, WP, thatmay be chosen to match a depth or width of the image 140 (when the image140 is a 3D image) such as several inches to several feet or be somewhatsmaller or larger and with a height, HP, that is chosen to place thesurface 152 at or just below a lower end or portion of the displayedimage 140. The pedestal 150 provides the viewers 104, 106 with contextor an anchor for perceiving the floating image 140 with more comfort orwith less eye strain that may occur when a floating image is provided ina disconnected manner in space.

Further, the image 140 may be caused to appear to have its source at thepedestal surface 152 by providing a lighting element or source 154 on ornear the surface 152 such that the image 140 appears to be a hologramoriginating from the lighting element 154. In other embodiments, theprop 150 may take other forms and the floating image 140 may be providedto emanate from and retract into one or more surfaces of the prop toachieve a desired visual effect. For example, the prop 150 may be arobot, a human actor, a futuristic character/statue, or the like and 2Dor 3D images 140 may be selectively displayed from one or more surfacesof such props (e.g., a light saber or light streak may appear from aprop's surface, a ghostly aura may be shown behind the prop, and so onas the use of floating images 140 is nearly limitless and only limitedby a designer of a display space 100 and display system 110).

The display system 110 is desirable for such display or viewing spaces100 as the displayed image 140 can be provided to be relatively brightso viewable in dark and also higher lighting settings (e.g., the space100 may be a lighted indoor space or even be outdoors with sunlightpresent). The display system 110 is also able to provide a relativelylarge image 140 with its height, H₂, ranging from several inched toseveral feet with its size limited mainly by the size of the imageryoutput from a display element 112 (which may be quite large dependingupon which technology is used to provide a 2D, 3D, or multi-layer image113).

To produce the image 140 (3D in this example), the display system 110includes a 3D display element 112 with an outer display surface 114, anddisplay element 112 is operated to display a 3D image 113 on thisdisplay surface 114 (or at the surface 114). For example, the displayelement 112 may be an LCD or similar display device operable to providea 3D image 113 on its display surface 114. This may be a high brightnessimage 113 such as by selecting the LCD or other display device to bedaylight-viewable (e.g., a device with luminance of 1500 to 2500 Nits orhigh levels of illuminance). Such high levels of luminance are desirablefor the display element 112 due to the losses in the display system 110such as at the beamsplitter 120 and because it is preferred that thedisplayed, floating image 140 be sharp and bright and be viewable inhigher light spaces 100 by viewers 104, 106. In other embodiments, a 3Dimage 113 is created through the use of a multiplane display element112, which also may be designed to provide the image 113 with highbrightness (higher luminance such as 2500 Nits or the like).

The outer display surface 114 is shown to be arranged to be facingdownward (e.g., the planar surface 114 is parallel to the floor/ground102 of the space 100) to project or display the image 113 downward asshown by arrows 116 (representing light emitted or projected fromdisplay element 112). In other embodiments, the surface 114 may beoriented differently such as to be vertical. The image 113 on displaysurface 114 (or from display element 112) has a size as shown by height,H₁, and the display system 110 is adapted such that the floating,displayed image 140 is a real image at display or focal plane 141 with asize matching that of the image 113, i.e., height, H₁, is equal toheight, H₂, of the image 140.

The display system 110 further includes a beamsplitter 120. The size ofthe floating image 140 matches that of output image 113 from displayelement 112 by having the distance, d_(A), from the upper or firstsurface 122 of the beamsplitter 120 to the display screen/surface 114matching the distance, d_(B), from the lower or second surface 124 ofthe beamsplitter to the image display or focal plane 141. Thebeamsplitter 120 is chosen to be large enough (e.g., with an adequatelylarge length, L, that is greater than a width of the display surface 114or at least greater than the height, H₁, of the image 113) such thatwhen it is arranged at an angle (e.g., 45 degrees as shown) to thedisplay surface 114 it can receive all (or most) of the light 116associated with the image 113. The beamsplitter 120 is transmissive tothe light 116 (as well as reflecting a portion off of the upper or firstsurface 122 away from the viewers 104, 106 and pedestal 150), and, as aresult, light 118 associated with the image 113 passes through thebeamsplitter 120.

Significantly, the display system 110 also includes a retroreflector (orretroreflective element) 130 positioned with its reflective surface 132facing the second or lower surface 124 of the beamsplitter 120 (and thedisplay element 112). In the illustrated embodiment, the retroreflector130 is mounted on a support stand or frame 131 so as to be planar andparallel to the display element surface 114 (as well as the floor 102),which results in the reflective surface 132 being at an angle (such as45 degrees) relative to the beamsplitter surface 124. The reflectedlight 133 from the retroreflector 130 strikes the lower or secondsurface 124 of the beamsplitter 120. A portion is reflected as shownwith arrows 135 while another portion is transmitted through thebeamsplitter 120 (not shown in FIG. 1). The light 135 acts to create orproduce the displayed, floating image 140, which in this example is a 3Dimage (still or video).

The retroreflector 130 may take many forms to practice the displaysystem 110 such as a sheet of retroreflective material (e.g., with a60-degree acceptance angle or the like) that is configured to reflectlight 113 back toward its source (e.g., the display element 112) with aminimum of scattering as shown with arrows 133 (e.g., reflected backalong a vector that is parallel to but opposite in direction from thesource light 118). The reflective surface 132 may include numerouscorner reflectors, Cat's eye reflectors, phase-conjugate mirrors, or thelike as found in conventional retroreflective material/sheets.

FIG. 1 illustrated use of a single retroreflector in combination with abeamsplitter and a 3D display element to provide a 3D displayed image.In other embodiments, it may be useful to add or change one or more ofthe components of the display system 100. For example, FIG. 2illustrates another display space or environment 200 with a secondembodiment of a display system 210. The display system 210 includesseveral of the components of the system 110, including the beamsplitter120 and the first retroreflector 130, and these are labeled with thesame reference numbers as in FIG. 1 and not described in as much detailwith reference to FIG. 2.

The display system 210 differs from system 110 in that it includes a 2Ddisplay element (such as a high luminance LCD or other monitor) 212operating to display a 2D image (still or video) 213 on its displayscreen/surface 214. The display system 210 is configured to provide afloating, real image 240 on the convergence plane 241 (the image andplane coincide in this case). Note, in display system 110, the displayelement 112 may be replaced with display element 212 and, likewise, thedisplay element 212 may be replaced in system 210 with the 3D displayelement 112. To this end, the system 210 (as with system 110) includes abeamsplitter 120 and a first retroreflector 130 positioned on anopposite side of the beamsplitter 120 to face the display element 212 toreflect the light 118 transmitted through the beamsplitter 120 backtoward the lower or second surface 124 of the beamsplitter 120. Thislight is reflected by the beamsplitter 120 as shown with arrows 133toward the convergence or display plane 241 to form the 2D displayedimage 240.

Additionally, though, this image 240 is increased in sharpness andbrightness by the inclusion of a second retroreflector 270. Thisretroreflector 270 is positioned to have its reflective surface 272facing and at an angle (e.g., 45 degrees) to the first or upper surface122 of the beamsplitter 120 (or to be orthogonal to the display surface214 and first reflective surface 132 of the first retroreflector 130).In this way, light 290 that is reflected from the first or upper surface122 of the beamsplitter 120 (a portion such as 50 percent of the light116 from the display element 212) strikes the reflective surface 272 ofthe second retroreflector 270. The retroreflector 270 functions toreflect this light (along parallel vectors) back through thebeamsplitter 120 as shown with arrows 295 to combine with rays/light 135from the first retroreflector 130 to form the 2D displayed (real) image240 for viewing by the viewers 104, 106 as shown at 105, 107. In thisway, the brightness (and sharpness) of the image 240 is increased (e.g.,80 to 100 percent) relative to the image 140 provided with a singleretroreflector 130.

The image 240 may further be enhanced by including a lens element 280with a single large lens or a plurality or array of many lenses (e.g.,microlenses that may be chosen to have an f number in the range of 6 to8 in some cases) on a surface 282 facing the first or upper surface 122of the beamsplitter 120. The lenses on surface 282 may be spherical,hexagonal, or varied in shape and size but with a matching (or the same)focal length. The lens element 280 is spaced apart from the reflectivesurface 272 of the retroreflector 270 as shown such as by one focallength. The lens element functions to sharpen the displayed image 240,e.g., by changing or reducing the entrance angle of the retroreflector270.

The display system 210 may further include one or more scrims 260 thatare hung or positioned between the beamsplitter 120 and the convergenceor display plane 241 for the displayed image 240. The scrim(s) 260 actsto allow a large percentage of the light 135 and 295, which incombination produce the displayed image 240, but also to block orreflect much of the ambient light in the space 200 so that the scrim 240appears as a relatively opaque wall. Hence, the scrim 260 acts todisguise or hide the components of the display system 210 from theviewers 104, 106 including the beamsplitter 120, the secondretroreflector 270, and the lens element 280. This further creates theillusion that the source of the floating image 240 is the lightingelement 154 of the anchoring prop or pedestal 150.

The lens element 280 (or micro lens element 580 in FIG. 5) serves auseful and important function in the display systems by focusing or“sharpening” the images produced by the display systems. In practice(due to manufacturing tolerances and other parameters), retroreflectorsdo not act to perfectly return or send one ray back toward the source oflight. Some small amount of light is instead returned within a cone, andthe amount of light in the cone will vary such as less than one percentto several percent of the received light. Stated differently blur can becaused by imperfections in the retroreflecting material as many of thereturned light rays are not collinear with the coming light ray due tothese imperfections (e.g., offset from being collinear by a fraction ofa degree which causes blur in the real image). This is a good enoughresult in many applications, but the inventors recognized that the useof sharpening or focusing elements (such as lens elements 280 and 580)are useful to try to get every or a greater amount of each ray toexactly go back toward the source to get a sharp and clear (or higherquality) real image. With this in mind, the inventors designed severalsharpening or focusing elements (or assemblies) that can be used in thedisplay systems of the present description such as in place of the lenselement 280 or lens element 580 or with any of the retroreflectors shownherein in the display systems.

In this regard, FIG. 6 illustrates a retroreflective sheet orretroreflector 630 that may be used in any of the display systemsdescribed herein (e.g., any of the retroreflectors of FIGS. 1-5). Asharpening or focusing element 650 is paired with the retroreflectivesheet 630 with a planar substrate or body (e.g., of transparent or atleast translucent material such as a glass, plastic, ceramic, or thelike) 652 arranged to be parallel to the sheet 630 and spaced apart asshown or in contact with the sheet 630. The sharpening element 650includes an array 660 of convex lenses 664 arranged in parallel rows andcolumns. The convex lenses 664 act to focus the light in each “cone”from the retroreflective sheet into more of a single ray to focus orsharpen the 3D floating image provided by a display system with theretroreflective sheet 630.

The lenses 664 may be conventional convex lenses as shown. In otheruseful or even preferred embodiments, the lenses 664 may take the formof Fresnel lenses as these may be easier to manufacture thanconventional convex lenses and easier to fabricate a large focusingelement or sheet (e.g., one that is up to 10 foot by 10 foot or larger).In still other implementations, the lenses 664 may be provided in theform of zone plates. In some cases, the convex lenses 664 are configuredto be astigmatic to provide preferential sharpening or focusing ineither the vertical or horizontal direction, which may be desirable insome applications to provide a sharper image in one direction. In stillother embodiments, the lenses 664 may be provided in the form ofcompound lenses (e.g., one or more lens per sheet area).

FIG. 7 illustrates another embodiment of a focusing or sharpeningelement 750 paired with a retroreflective sheet 630. In thisimplementation, the element 750 has its transparent body or substrate752 mated with the retroreflective sheet 630 to be in contact with itsupper surface (or the lenses 764 may be formed on the retroreflectivesheet 630 in some cases). The sharpening element 750 includes an array760 of convex lenses 764 as in the array 650 of FIG. 6. However, thelenses 764 vary from the lenses 664 in that they differ in size (and/orshape) and are arranged in a random or more random pattern than in thearray 660 (note, it may be useful to have the lenses be of equal sizebut be arranged in a random pattern with this particular arrangement notshown in the figures but understood by those skilled in the art). Aswith the array 660, the lenses 764 may be conventional convex lenses,Fresnel lenses, or zone plates. Also, the lenses 764 can be astigmaticand/or compound.

FIG. 8 illustrates another embodiment of a sharpening or focusingelement 850 that may be used or paired with a retroreflective sheet 630in one of the display systems of the present description. As shown, thesharpening element 850 comprises a substrate of a transparent (or atleast translucent) material in which an array of lenses 864 in the formof lenticular lenses (or elongated, cylindrical lenses). The lenses 864receive diverging light 870 from the retroreflective sheet 630 andsharpens the light as shown at 872 to be between two parallel lines(rather than spreading out in a cone). The lenses 864 are labeled asvertical or for use in providing vertical sharpening of light such as ifplaced in a vertical position in place of lens element 280 in FIG. 2.However, the lenticular lenses 864 may be rotated 90 degrees to providehorizontal sharpening or focusing such an application. The lenticularlenses 864 may be thought of as an extreme example of an astigmatic lensarray as they do not provide the same magnification in either direction.Note, the lenses 864 are not shown to scale, and the focusing element850 typically would include many more lenticules 864 (or at a muchhigher density) in practice.

FIG. 9 illustrates another focusing element 950 that may be positionedbetween a retroreflector 630 and a beamsplitter 990 of a display system(e.g., those shown in FIGS. 1-5) of the present description. Thefocusing element 950 is formed with an opaque (or less transparent tolight) substrate 952 and an array 960 of elongated slits (or slots) 964(e.g., extend substantially from one end to the other of the substrate952) are formed or cut in this substrate 952 between bars 965 of thematerial of the substrate 952. In this way, light reflected back fromthe retroreflector 630 is sharpened or focused in one direction as itpasses through the slits 964. The slits 964 may be considered verticalslits (e.g., oriented so as to be vertical in respect to the projectedreal image) such as when the element 950 is arranged vertically in placeof lens element 280 in FIG. 2, and used to sharpen horizontalretroreflection. This is shown in FIG. 9 with the cone 970 showing widerhorizontal diffusion that would have resulted without the use of thefocusing element 950 and with the cone of light 980 that has a narrowedhorizontal retroreflected light swatch provided by the slits 964.

In other embodiments, the slits may be rotated 90 degrees to providehorizontal slits used to sharpen vertical retroreflection. Thisembodiment is shown in FIG. 10 with the focusing element 1050 with anopaque substrate 1052 and an array 1060 of slits 1064 (between bars 1065of substrate material) oriented horizontally with respect to theprojected real image. This focuses the retroreflected light from a widecone 1070 to a narrower vertical swath 1080. As with the lenticules 864of FIG. 8, the slits 964 are not shown to scale and typically would begreater in number/density, and the size (width) of the slits 964 mayvary widely to practice the focusing element 950.

FIG. 11 illustrates another useful focusing or sharpening element 1150that may be paired with a retroreflective surface 630 to providespatially variable sharpening of the retroreflection. The sharpeningelement 1150 may be implemented using an addressable spatial lightmodulator (such as a liquid crystal display (LCD) or the like) with itsscreen 1152 selectively operated to be opaque or transparent to thelight from the retroreflective sheet 630. In the non-limiting exampleshown in FIG. 11, the display screen/surface 1152 is configured todisplay first and second arrays of slits 1160, 1162 (e.g., alternatingpatterns of transparent slits and opaque bars) for providing horizontal(or vertical in other embodiments) sharpening of light from theretroreflector 630 as discussed with reference to FIG. 9).

Further, a row 1160 of pin-holes 1166, which may have nearly any desiredsize/diameter, are displayed between the slit arrays 1160, 1162 andprovide transparency at the pin-holes 1166 and are opaque in the rest ofthe row 1160 (between the pin-holed 1166). The result of the use of thepin-holes 1166 is shown with the wide retro-reflected swath 1170 thatwould have occurred without the holes 1166 and with the narrowedretroreflected swath 1180 with the surface apertures or pin-holes 1166.With the use of the addressable spatial light modulator screen 1152 thelocations and configurations (sizes, vertical versus horizontal, and soon) of the slit arrays 1160, 1162 and apertures 1166 are not fixed(e.g., pattern of slits and holes is not fixed or limiting of thefocusing element 1150) and can vary to suit a particular display systemor be varied over time (e.g., with a changing 3D real image or toachieve time varying visual effects). For example, narrower slits in thearrays 1160, 1162 may be used to provide increased sharpening of a realimage over time.

In some cases, the light being directed toward the retroreflector may bepolarized light. In such cases, the focusing element 1250 may take theform shown in FIG. 12 with a substrate or sheet 1252 of polarizedmaterial. Then, an array 1260 of vertical slits or columns 1262 may becut out of or formed in the substrate 1252. The retroreflector 630 inthis case is chosen so as to provide a polarization maintainingretroreflective surface. Then, the focusing element 1250 acts to providepreferential sharpening of polarized light with the slits or columns1262 as shown with the unpolarized light (or light with a polarizationin a second direction) 1270 is output in a wider cone or swath while thepolarized light aligned with the polarizer sheet 1252 is sharpened orfocuses within narrower swath or cone 1280.

Similarly, it may be desirable in some cases to provide color-selectivesharpening. To this end, light from a source may include a least firstand second colors (such as red and blue light), and it may be desirableto provide selective focusing or sharpening of the first color (or redlight, in this non-limiting example) as it is retroreflected. FIG. 13shows a focusing or sharpening element 1350 with a substrate or sheet1342 of material that is transparent to the second color (to the bluelight), and an array 1360 of slits 1364 are provided that aretransparent to the first color (to the red light). In this way, thefocusing element acts to selectively narrow or sharpen the first color(or the red light). This can be seen with the wider swath or cone ofretroreflected light of the second color (or blue light) so that thislight stays “blurry” while a narrowed retroreflected swath 1380 isprovided by the slits 1364 so that the first color (or red light in thisexample) is sharpened to provide color-selective sharpening with thefocusing element 1350.

The inventors recognized that observers of the display system may beable to perceive the existence of the sharpening or focusing elementsuch as due to the patterns of the lenses or slits or may be able to seeseams in the retroreflective material if smaller panels or sheets areassembled together to create a much larger sheet. To hide or disguisethe presence of these components, it may be useful in some displaysystems to provide translation or translational movement of thesharpening element alone or along with the retroreflective sheet.

FIG. 14 illustrates such a disguising or hiding embodiment with atranslation assembly 1410 included to apply a translational motion 1412,1413 to the focusing element 950 (alone or with the retroreflectivesheet 630 if these two components are rigidly coupled together). Thetranslation assembly 1410 may be configured to shake or vibrate thefocusing element 950 to move the element 950 back and forth (in arelatively rapid manner or oscillating frequency) as shown with arrows1412, 1413. In other cases, though, the focusing element (and, in somecases, the retroreflector 630) may be rotated by the translationassembly 1410 such as by applying the retroreflector 630 and focusingelement 950 to a cylinder that is rotated or by providing the focusingelement 950 as a large disc (with or without the retroreflector 630)rotated about a central axis. Other ways of translating the focusingelement 950 may be used, and translation assembly 1410 may be used withthe other focusing or sharpening elements to hide the focusing orsharpening elements (or seams in the retroreflector) such as by hidingpresence of individual slits or lenses.

FIG. 15 illustrates another useful focusing element 1550 that may beused with a horizontally arranged retroreflector 630 (such asretroreflector 130 in the display system 500 of FIG. 5) to provideclarifying or sharpening lenses. As shown, the retroreflective sheet ormaterial 630 is provided as backing or a back plate for a liquidcontainer 1552, which is shown to be in the form of four sidewallsdefining a void or space. This void or space in the container 1552 isfilled with a volume of a liquid 1554 (such as water) with desiredoptical properties. A sheet of perforated sheet or screen 1556 islowered into or positioned in the liquid 1554 so as to be generallyparallel to the retroreflector 630 (and upper surface of the liquid1554). An array of liquid lenses 1558 is formed by surface tension asthe perforated sheet 1556 is lowered on the surface of the liquid 1554,and these lenses 1558 act in a manner similar to convex lenses of thefocusing element 650 to sharpen or clarify the real image formed withthe retroreflector 630. The clarify of the real image can be varied inpractice with the focusing element 1550 by moving the perforated sheetto differing depths relative to the upper/outer surface of the liquid1554, with the image being clearer when the lenses 1558 are more curvedand being less clear if lenses 1558 are flattened.

FIG. 3 illustrates another embodiment of a display system 310 that isshown to be operating to produce or generate a displayed real image 360to a viewer 302, with only a single retroreflector. In this embodiment,the viewer 302 observes the image 360 through special eyewear 370 in theform of polarized glasses or the like. In this regard, the displayelement 312 is configured to output or display an image on its displaysurface 314 with light 316 having a first polarization. The imagedisplayed in screen 314 by display element 312 may be a 2D or a 3D imageprovided as a still or video image.

A beamsplitter 320 is positioned with a first or upper surface 322facing the display element 312 at an angle (e.g., 45 degrees). Some ofthe light 316 is reflected away from the viewer (e.g., 50 percent), butthe beamsplitter 320 is polarized (or configured) to be transmissive tolight having the first polarization such that another portion orfraction (e.g., 50 percent) is transmitted through as shown with arrows326. The display system 310 further includes a one-quarter waveplate 330and a retroreflector 340 with its reflective surface 342 facing thebeamsplitter 320 (e.g., with the surface 342 parallel to the planardisplay screen/surface 314). The waveplate 330 is disposed between thelower or second surface 324 of the beamsplitter 320 and theretroreflective material element 340.

During operation of the display system 310, the light 326 from thebeamsplitter 320 passes through the waveplate 330 and its polarizationis rotated 90 degrees (or a quarter turn) such that the light 335striking the reflective surface 342 has a second polarization differingfrom the first polarization of the original image light 316. Theretroreflector 340 reflects this light as shown 345 causing it to againpass through the ¼ waveplate 330, which acts to modify or rotate thepolarization again by 90 degrees or a quarter turn such that the light355 from the retroreflector 340 that strikes the second or lower surface324 of the polarized beamsplitter 320 has a third polarization differingfrom both the first polarization and the second polarization.

The beamsplitter 320 is configured to not be transmissive to light withthis third type of polarization (e.g., light not having the firstpolarization as found in light 316 from display element 312), and, as aresult, as shown with arrows 357, all or a large percentage of the light355 is reflected into a display space to produce or generate thedisplayed image 360. This image 360 can then be viewed by the viewer 302with eyewear 370 adapted for viewing light with the third polarization.When compared with system 110 with its single retroreflector 120, thedisplay system 310 is able to provide a brighter image 360 with adisplay element 312 having the same luminence capability as the displayelement 112 as less light is lost via the beamsplitter 322 as is thecase with beamsplitter 120.

In some cases, it may be desirable for the image to be displayed in amanner that is interactive with the viewer 104 and/or 106. FIG. 4illustrates an interactive display space or environment 400 includinganother embodiment of a display system 410, which builds upon andmodifies the display system 110 (with similar components shown with likereference numbers). In other cases, though, the modifications shown tosystem 110 may be applied to system 210 or system 310 or a combinationof systems 110, 210, 310, and 410 may be made to rearrange and/or usediffering sets of the various components taught herein to provide adesired visual effect.

To this end, the display system 410 includes a viewer tracking assembly490 that senses as shown with arrows 492 a location and/or movement ofthe viewer 104 relative to the location of the convergence or displayplane 141 and displayed image 140. The tracking assembly 490 may takemany forms to practice the display system 410 such as a motion or videotracking hardware and software as will be well understood by thoseskilled in the arts. The tracking assembly 490 responds to theposition/motion tracking 492 to transmit interaction data to acontroller 460 as shown with wired or wireless signals 494.

The controller 460 may take the form of a computing or electronic devicewith a processor 462 for managing/running input/output (I/O) devices 464such as a wireless transceiver for receiving the communications 494 fromthe viewer tracking assembly 490. The controller 460 also is shown toinclude (or have access to) memory or data storage devices 470 thatstore, under control of the CPU 462, the received interaction data 472and also one or more images/video streams 474.

The memory 470 may also store executable code or programminginstructions that are executed or performed by the processor 462 toprovide the functionality of a display program 466. This functionalityincludes processing the interaction data 472 about the viewer 104 andtheir interaction with the displayed image 140 and, in response,generating control signals 467 causing the display element 112 tooperate to display an image 113 using (or by playing) one or more of theimages/image streams 474 (which are chosen or modified based on theinteraction data 472). In this manner, a user/viewer 104 can interact ina live manner (e.g., to play a game, to operate/change a displayedcontrol panel, and so on) with the displayed image 140 and/or any props150 in the display space or environment 400. This is achievable in someregards because the exact location of the displayed image 140 and/orconvergence plane 141 is a known value for the display program 466 (andmay be stored in memory 470) such that the viewer's position is relativeto the displayed image 140.

FIG. 5 shows another useful embodiment of a display environment or space100 in which a display system or apparatus 510 of the presentdescription is operating to display a floating 2D or 3D image 560 to aviewer 502. The floating image 560, as in the system 110 of FIG. 1, maybe displayed over a top surface of a prop in the form of a pedestal ortable to provides the viewer 502 with context or an anchor forperceiving the floating image 560 with more comfort or with less eyestrain that may occur when a floating image is provided in adisconnected manner in space. Further, as in system 110, the image 560may be caused to appear to have its source at the pedestal surface byproviding a lighting element or source on or near the surface such thatthe image 560 appears to be a hologram originating from the lightingelement.

To produce the image 560 (2D or 3D in this example), the display system510 includes a 2D or 3D display element 512 with an outer displaysurface or the like, and display element 512 is operated to display a 2Dor 3D image 513 (e.g. at the outer display surface or with multi-layeror planar display screens or the like). For example, the display element512 may be an LCD or similar display device operable to provide a 2D or3D image 513 on its display surface. This may be a high brightness image513 such as by selecting the LCD or other display device to bedaylight-viewable (e.g., a device with luminance of 1500 to 2500 Nits orhigh levels of illuminance). The display element 512 is shown to bearranged to be facing downward (e.g., its display screen is parallel tothe floor/ground of the space 500) to project or display the image 513downward as shown by arrows 516 (representing light emitted or projectedfrom display element 512). In other embodiments, the display elementsurface 114 may be oriented differently such as to be vertical or at anyuseful angle relative to the other system components.

The display system 510 further includes a beamsplitter 120. The size ofthe floating image 560 matches that of output image 513 from displayelement 512 by having the distance from the upper or first surface 122of the beamsplitter 120 to the display screen/surface matching thedistance from the lower or second surface 124 of the beamsplitter 120 tothe image display or focal plane (as explained in detail with referenceto FIG. 1). The beamsplitter 120 is chosen to be large enough (e.g.,with an adequately large length, L, that is greater than a width of thedisplay surface 114 or at least greater than the height, H₁, of theimage 513) such that when it is arranged at an angle (e.g., 45 degreesas shown) to the display element 512 it can receive all (or most) of thelight 516 associated with the image 513. The beamsplitter 120 istransmissive to the light 516 (as well as reflecting a portion off ofthe upper or first surface 122 away from the viewer 502, and, as aresult, light 516 associated with the image 513 passes through thebeamsplitter 120.

Significantly, the display system 510 also includes a retroreflector (orretroreflective element) 130 positioned with its reflective surface 132facing the second or lower surface 124 of the beamsplitter 120 (and thedisplay element 512). As discussed for system 110 of FIG. 1, theretroreflector 130 may be mounted on a support stand or frame so as tobe planar and parallel to the display element 512 (or its displayscreen(s)/layer(s)) (as well as the floor of space 500), which resultsin the reflective surface 132 being at an angle (such as 45 degrees)relative to the beamsplitter surface 124. The reflected light 133 fromthe retroreflector 130 strikes the lower or second surface 124 of thebeamsplitter 120. A portion is reflected as shown with arrows 585 whileanother portion is transmitted through the beamsplitter 120 (not shownin FIG. 5). The light 585 acts to create or produce the displayed,floating image 1560, which in this example may be a 2D or 3D image(still or video).

The display system 510 differs from system 110 in another significantway. The system 510 includes a micro lens element 580 in the form of asheet or array of lenses. The micro lens element 580 is positionedbetween the lower or second surface 124 of the beamsplitter 120 and thereflective surface 132 of the retroreflector 130. In this embodiment,the micro lens element 580 is a planar sheet or pane and is arranged tobe parallel to the reflective surface 132. It receives the light 133reflected from the retroreflector 130 and passes this light as shown at584 to the second or bottom surface 124 of the beamsplitter 122 where itis reflected as the light 585 that produces displayed image 560. Themicro lens element 580 may be spaced apart from the reflective surface132 by a relatively small distance such as 1 to 12 inches with a spacingin the range of 2 to 4 inches used in some prototyped embodiments.

The micro lens element (e.g., an array or sheet of micro lenses) 580 maytake a variety of forms to practice the display system 510. The microlens element 580 is chosen and/or configured to act or function toclarify the displayed image 560 compared to a display system withoutsuch as micro lens element in which the image may look less clear oreven blurry (which may be a useful or desired result, though, in manyapplications as it provides a unique “ghostly” effect). The resultingincrease in clarity can be surprisingly large such as the displayedimage 560 being 2 to 10 times (or more) clearer than in the system 510without the micro lens element 580. The micro lens array 580 may includea random pattern of small lenses so that the human eye typically willnot pick up a repeating pattern in the displayed image 560.

FIG. 16 illustrates another embodiment of a display system 1600 thatmakes use of two lenses 1620, 1660 along with two retroreflectors 1640,1650 to achieve a floating image with light/rays 1664 from second lens1660. In system 1600, the display 1610 displays an image causing lightor rays 1612 to be transmitted onto a first lens 1620, which focuses thelight 1622 onto a first side/surface of a beamsplitter 1630. A portion1630 of the light 1622 passes through the beamsplitter 1630 onto one ofthe retroreflectors 1640 to provide retroreflection 1642 back toward thesecond side/surface of the beamsplitter 1630, where it is reflected aslight 1656 to the second lens 1660 for focusing as shown at 1664 toprovide a floating image viewable by a viewer (not shown). The light1656 directed toward the second lens 1660 also includes retroreflection1652 passing through the beamsplitter 1630 from another retroreflector1650 provided by light 1646, which is light 1622 from the first lens1620 that is reflected by the first side/surface of the beamsplitter1630.

As can be seen in FIG. 16, two lenses 1620, 1660 (i.e., one before thebeamsplitter 1630 and one after) are used rather than a double passthrough a single lens or lenslet array in front of the retroreflector.The retroreflected double pass through a single lens is self-correctingto aberrations (any aberrations introduced during the first pass throughthe lens is corrected by the light following the same path back throughthe lens in the opposite direction). Passing through two differentlenses 1620, 1660 (one before the beamsplitter 1630 and one after) has asimilar effect (although not as perfectly, since there may be slightvariations between the lenses). The lenses 1620, 1660 typically would belarger lenses or coarse arrays because they still need to focus on theretroreflector sheet 1640 or 1650. The large lenses 1620, 1660 clarifythe image provided by light/rays 1664 while also keeping the system 1600relatively compact (as the lens/retroreflector spacing is not all behindthe beamsplitter 1630).

FIG. 17 illustrates another embodiment of a display system 1700 that isconfigured to provide a pancake retroreflective real image 1760. To thisend, the system 1700 includes a polarized display 1710 that passes lightthrough a stack or optical stack prior to striking a beamsplitter 1730positioned (e.g., at 45 degree angles) between first and secondretroreflectors 1740, 1750. The optical stack includes a first quarterwave plate (e.g., +45 degrees) 1712 proximate to the display 1710, ahalf mirror 1714, a second quarter wave plate (e.g., +45 degrees (whilesome embodiments may use a −45 degrees quarter wave plate combined withwave plate 1712)) 1716 distal to the display 1710 (with the half mirror1714 sandwiched between the two quarter wave plates 1712, 1716), and areflective polarizer 1720 proximate to the beamsplitter 1720. Thepolarization states within this stack are shown with graph 1705.

The optical stack in the display system 1700 of FIG. 17 is a stack ofwave plates and polarizing beamsplitters that cause the light or pathfrom display 1710 to bounce back and forth on itself to reduce the pathlength, e.g., like “pancake optics” used in flight simulator collimators(whereas display system 1700 uses an arrangement for relaying an objectto form a real image and without an imaging or relay lens element). Oneof the issues with retroreflectors that was identified by the inventorsis that the object and image are 1:1, and, as a result, the distance ofthe real image from the beamsplitter is the same distance from theobject to the beamsplitter. This can cause the size of the displaysystem to become bulky and burdensome in some cases. Using the stack ofwave plates and polarizer as shown in FIG. 17 can shrink the size of thesystem 1700 as the distance from the object (display 1710) to thebeamsplitter 1720 can be reduced by two-thirds of the distance (withoutuse of the optical stack). This occurs before the beamsplitter (and lensarray/lens element and retroreflector). It also does not involve or passthrough a lens element to form a real image, and it can in someimplementations only involve film sheets after the display 1710 suchthat it should be scalable.

FIGS. 18A-18D illustrate an additional useful embodiment of a displaysystem 1800 that combines the efficient display system of FIG. 3 thatused a polarization beamsplitter and a quarter wave plate with thecompact pancake retroreflective system of FIG. 17 to obtain a newcompact and efficient retroreflective real image (in a display spacewith light/rays 1860 in FIGS. 18A-18D). FIG. 18A illustrates the overallsystem 1800 as it operates to provide the real image while FIGS. 18B-18Dillustrate effects or changes to the light from the display 1810 as itpasses through or is reflected from each optical component of thedisplay system 1800.

As shown, the display system 1800 includes a polarized display 1810outputting or displaying imagery as shown with light/rays 1812 thatstrikes a first surface of a polarization-sensitive beamsplitter 1820.The light 1812 is transmitted through the beamsplitter 1820 as shown at1822 where it is received/strikes a combination of a first quarter waveplate (e.g., +45 degrees) and a mirror 1834. The light 1836 is reflectedback toward the second surface of the beamsplitter 1820 where it isreflected as shown at 1838 toward a combination of a second quarter waveplate 1840 (e.g., +45 degrees) and a retroreflector 1850. Theretroreflection or light 1852 is then transmitted back to the secondsurface of the beamsplitter 1820, and it passes through as shown at 1860to form a real image (e.g., a space/location where the light/rays 1860are focused) viewable by a viewer (not shown) in a display space.

As shown, the polarized display light 1812 passes through (as shown at1822) through the polarization-sensitive beamsplitter 1820. It thenpasses through a quarter wave plate 1830 and reflects off a mirror 1834,which creates a virtual display below the beamsplitter 1820 and changesthe polarization from horizontal to circular (in this example). Thereflected light 1836 passes back through the quarter wave plate 1830changing the polarization from circular to vertical. The light 1836 (nowshown as 1838) then bounces off the polarization-sensitive beamsplitter1820 and passes through a second quarter wave plate 1840 (changing thelight from vertical to circular polarization) to a retroreflector 1850.The retroreflector 1850 sends the light 1852 back toward where it camefrom and rotates its polarization again (e.g., from circular tohorizontal), which can then pass through the polarization-sensitivebeamsplitter 1820 as shown at 1860 to form a real image twice (or more)as far from the beamsplitter as the distance between beamsplitter 1820and the display 1810. The real image is formed without the loss of lightthrough the beamsplitter 1820, as may be the case in some other displaysystem embodiments. Hence, the display system 1800 removes theinefficiency of the half-mirror of the pancake version (e.g., system1700 in FIG. 17) and makes the efficient version (e.g., system 300 inFIG. 3) more compact.

In some cases, it may be desirable to avoid the 90-degree bend in system1800 of FIGS. 18A-18D and, instead, provide an inline arrangementbetween the display element and the display space or real imagelocation. FIG. 19A shows such a system 1900 with FIGS. 19B-19D (similarto FIGS. 18B-18C) showing polarization states as the light passesthrough the display system 1900. As shown, the display system 1900includes a polarized display 1910 that is oriented to face outward to adisplay space and a location planned for a displayed real image 1960. Apolarization sensitive beamsplitter 1920 is provided in the system 1900,and output light (polarized light providing the display's image) 1912from the polarized display 1910 is directed onto a first surface of thebeamsplitter 1920.

Due to its polarization, the light 1912 is reflected as shown at 1922toward a combination of a quarter wave plate (e.g., +45 degrees) 1930and a mirror 1932. These two components 1930 and 1932 may be parallel toeach other and orthogonal to the display 1910. Light 1936 reflected fromthe mirror 1932 (and passing twice through wave plate 1930) is directedback towards the first surface of the beamsplitter 1920, where due toits changed polarization it is passed or transmitted through as shown at1938. The light 1938 is directed toward a combination of a secondquarter wave plate (e.g., +45 degrees) 1940, an optional micro lensarray or lens element 1942 for sharpening the imagery, and aretroreflector 1944. These three components may also be parallel to eachother and also to the first quarter wave plate 1930 and mirror 1932(e.g., the mirror 1932 faces the retroreflector 1944). The light orretroreflection 1946 from the retroreflector 1944 (which has passedtwice through the wave plate 1940) is directed back toward the mirror1932 where it strikes the second surface of the beamsplitter 1920. Dueto its changed polarization, it is reflected as shown at 1950 from thebeamsplitter 1920 and acts to generate a real image 1960 at a desiredlocation in the display or viewing space of system 1900.

The display system 1900 efficiently provides a retroreflective realimage 1960 inline with display 1910, and the display system 1900 iscompact. It is desirable to provide an inline arrangement at least forthe reason that most lenses and other 1:1 imaging devices presently inuse are inline. Use of a 90-degree bend can make a display system morecumbersome, e.g., the display may need to be suspended and facing thefloor. In the imaging or display system 1900, the system acts more likea normal imaging lens except with no aberrations (except for theretroreflective blurring, which can be fixed with the use of theoptional micro lens array 1942). Significantly, the distance from thereal image 1960 to the beamsplitter 1920 is three times the distancebetween the display 1910 and the beamsplitter 1920, which means thedisplay system 1900 is very compact (relative to other displayarrangements shown herein, for example). The use of quarter wave plates1930, 1940 and the polarization-sensitive beamsplitter 1920 makes thedisplay system 1900 efficient (e.g., when compared with display system1700 of FIG. 17). Each component in the display system 1900 may beimplemented as a film so that the display system 1900 should be readilyscalable.

Although the invention has been described and illustrated with a certaindegree of particularity, it is understood that the present disclosurehas been made only by way of example, and that numerous changes in thecombination and arrangement of parts can be resorted to by those skilledin the art without departing from the spirit and scope of the invention,as hereinafter claimed.

For example, a 2D or 3D display element may include an LED chase or rowthat may be operated to sequentially illuminate a plurality of LEDs toprovide a moving or changing streak of light or another illuminatedshape or object at the convergence or display plane in the viewingspace. This real, displayed image can be provided at a known locationrelative to a portion or surface of a prop positioned a predefineddistance (e.g., a distance, d_(B), from the second or lower surface ofthe beamsplitter as shown in FIG. 1) in the display space. Any distance,d_(B), may be used, but one in the range of 3 to 10 feet (closer ratherthan farther away) may be desirable to provide a clearer orsharper-focused displayed image.

In some embodiments, the display system is configured to spin both areflector and a lens/lens array together. In this way, the spinning lensarray (or half of a disc could be used) does not have to be edge drivento keep the center of the lens array clear. With both retroreflector andlens/lens array spinning together, the shaft can be centered behind both(which is easier to do than edge driving). Also, the display system hasa clear center (e.g., no obstructing drive shaft), and the displaysystem hides both retroreflector and lens seams when spun fast enough orat high enough speeds.

In other display system arrangements, a strip of the retroreflector isspun with or without a lens or lens array. This is similar to atransparent retroreflector real image. For example, it may be desirableto use a transparent retroreflector (combined with projectors) for HUDS(heads up displays or heads up display systems), but it would also beinteresting for a real image character that does not appear in front ofa retroreflective backdrop and/or scrim that would just appear in frontof any background. A beamsplitter is still provided in front of thespinning strip of retroreflector. Note, there are other transparentretroreflectors, e.g., the corner cube array that is not metallized or abunch of concave divots in a plastic sheet.

We claim:
 1. An apparatus for generating floating images, comprising: adisplay element displaying an image with first light from a displaysurface; a retroreflector comprising a reflective surface facing thedisplay surface and including a retroreflective material; a beamsplitterdisposed between the display element and the retroreflector with a firstsurface facing the display surface to receive the first light; and aprop in the display space with a surface below, above, or to the side ofthe displayed image, wherein at least a portion of the surface of theprop is located at a separation distance from the second surface of thebeamsplitter that equals the distance between the displayed image andthe second surface of the beamsplitter, wherein the beamsplittertransmits a portion of the received first light as second light towardthe reflective surface of the retroreflector, wherein the reflectivesurface reflects the second light as third light toward a second surfaceof the beamsplitter that is opposite the first surface, and wherein thebeamsplitter reflects a portion of the third light as fourth light intoa display space to provide a displayed image at a distance from thesecond surface of the beamsplitter.
 2. The apparatus of claim 1, whereinthe reflective surface and the display surface are planar surfaces,wherein the reflective surface is parallel to the display surface, andwherein the first surface of the beamsplitter extends at an angle of 45degrees relative to the display surface.
 3. The apparatus of claim 1,wherein the displayed image is a real image provided at a convergenceplane located the distance from the second surface of the beamsplitter.4. The apparatus of claim 3, wherein the first surface of thebeamsplitter is located a second distance, equal to the distance fromthe second surface of the beamsplitter, from the display surface.
 5. Theapparatus of claim 1, further comprising a focusing element positionedbetween the second surface of the beamsplitter and the reflectivesurface of the retroreflector, the focusing element being adapted toclarify the displayed image.
 6. The apparatus of claim 5, wherein thefocusing element comprises a planar array of convex lenses of differingsizes arranged in a random pattern.
 7. The apparatus of claim 6, theplanar array is positioned to be parallel to the reflective surface ofthe retroreflector at a distance of less than 12 inches.
 8. Theapparatus of claim 5, wherein the focusing element comprises an array ofconvex lenses.
 9. The apparatus of claim 8, wherein the convex lensesare Fresnel lenses or zone plates.
 10. The apparatus of claim 8, whereinthe convex lenses are astigmatic or compound.
 11. The apparatus of claim5, wherein the focusing element comprises a sheet of lenticularmaterial.
 12. The apparatus of claim 5, wherein the focusing elementcomprises a sheet of opaque material including an array of elongated,side-by-side slits formed in the opaque material to transmit lightthrough the focusing element and wherein the elongated, side-by-sideslits are arranged to provide sharpening of vertical retroreflection orhorizontal retroreflection.
 13. The apparatus of claim 5, wherein thefocusing element comprises an addressable spatial light modulatorselectively operable to concurrently display an opaque pattern and atransparent pattern and wherein the transparent pattern includes atleast one of an array of transparent slits and a pattern of transparentapertures.
 14. The apparatus of claim 5, wherein the focusing elementcomprises a sheet of polarized material with horizontal or verticalcolumns to provide sharpening of light of a predefined direction ofpolarization in the third light from the retroreflector and wherein thereflective surface of the retroreflector comprises a polarizationmaintaining retroreflective surface.
 15. The apparatus of claim 5,wherein the focusing element comprises a substrate of materialtransparent to light of a first color and an array of vertical orhorizontal slits in the substrate that are transparent to light of asecond color, whereby rays of the second color are sharpened by thefocusing element.
 16. The apparatus of claim 5, further comprising atranslation assembly applying a translational motion to the focusingelement.
 17. The apparatus of claim 16, wherein the translational motionis vibration or rotation.
 18. The apparatus of claim 16, wherein theretroreflector is coupled to the focusing element whereby thetranslational motion is concurrently applied to the retroreflector bythe translation assembly.
 19. The apparatus of claim 5, wherein thefocusing element comprises a liquid container, a volume of liquiddisposed in the liquid container, and a perforated sheet disposed in thevolume of liquid to a depth, whereby an array of liquid lenses areformed for focusing the third light.
 20. The apparatus of claim 1,wherein the display element comprises a monitor with an output luminenceof at least 2500 Nits.
 21. The apparatus of claim 20, wherein thedisplay element comprises a liquid crystal display (LCD) monitor. 22.The apparatus of claim 1, wherein the display element is a monitor ormulti-level display assembly and wherein the image is athree-dimensional (3D) image.
 23. The apparatus of claim 1, wherein theretroreflector comprises a strip of the reflective material with atranslation assembly spinning the strip to provide the reflectivesurface facing the display surface.
 24. The apparatus of claim 1,further comprising a second retroreflector positioned with a reflectivesurface including retroreflective material facing the first surface ofthe beamsplitter and oriented to be orthogonal to the reflective surfaceof the retroreflector.
 25. The apparatus of claim 24, further comprisinga lens element disposed between the reflective surface of the secondretroreflector and the first surface of the beamsplitter, wherein thelens element is positioned a distance from the reflective surface of thesecond retroreflector that is equal to a focal distance of one or morelenses of the lens element.
 26. The apparatus of claim 25, furthercomprising first and second lenses, wherein the first lens is disposedbetween the display element and the beamsplitter to focus light from thedisplay element onto the retroreflector and the second lens is disposedbetween the beamsplitter and the display space to focus light from thebeamsplitter to sharpen the displayed image.
 27. The apparatus of claim1, further comprising a scrim positioned between the second surface ofthe beamsplitter and the display space.
 28. The apparatus of claim 1,wherein the first light from the display element has a firstpolarization, wherein the beamsplitter is polarized to be transmissiveto light having the first polarization and to reflect light with otherpolarizations, wherein the apparatus further comprises a waveplatebetween the second surface of the beamsplitter and the reflectivesurface of the retroreflector, wherein the second light has a secondpolarization and the third light has a third polarization, and whereinthe third polarization differs from the first polarization.
 29. Adisplay system, comprising: a display displaying a 2D or 3D image; aretroreflector with a planar reflective surface facing the display toreflect the 2D or 3D image; a beamsplitter disposed between the displayand the reflective surface of the retroreflector, wherein thebeamsplitter is oriented at an angle relative to the reflective surfacewhereby a first surface of the beamsplitter faces the display and asecond surface opposite the first surface faces the reflective surfaceto reflect light from the reflective surface into a display space,whereby a floating image corresponding to the 2D or 3D image isdisplayed in the display space; and a second retroreflector with aplanar reflective surface oriented to be orthogonal to the reflectivesurface of the retroreflector and to face the first surface of thebeamsplitter.
 30. The display system of claim 29, further comprising afocusing element spaced apart from and parallel to the planar reflectivesurface of the retroreflector, whereby the focusing element ispositioned between the retroreflector and the beamsplitter.
 31. Thedisplay system of claim 30, wherein the focusing element comprises aplanar array of convex lenses arranged in a random pattern.
 32. Thedisplay system of claim 31, the planar array is positioned to beparallel to the reflective surface of the retroreflector at a distanceof less than 12 inches and the convex lenses differ in size or shape.33. The display system of claim 30, wherein the focusing elementcomprises an array of convex lenses that are at least one of Fresnellenses, zone plates, astigmatic, and compound.
 34. The display system ofclaim 30, wherein the focusing element comprises an array of elongated,side-by-side, cylindrical lenses on a transparent substrate.
 35. Thedisplay system of claim 30, wherein the focusing element comprises asheet of opaque material including an array of elongated, side-by-sideslits formed in the opaque material to transmit light through thefocusing element and wherein the elongated, side-by-side slits arearranged to provide sharpening of vertical retroreflection or horizontalretroreflection.
 36. The display system of claim 30, wherein thefocusing element comprises an addressable spatial light modulatorselectively operable to concurrently display an opaque pattern and atransparent pattern and wherein the transparent pattern includes atleast one of an array of transparent slits and a pattern of transparentapertures.
 37. The display system of claim 30, wherein the focusingelement comprises a sheet of polarized material with horizontal orvertical columns to provide sharpening of light of a predefineddirection of polarization from the retroreflector and wherein thereflective surface of the retroreflector comprises a polarizationmaintaining retroreflective surface.
 38. The display system of claim 30,wherein the focusing element comprises a substrate of materialtransparent to light of a first color and an array of vertical orhorizontal slits in the substrate that are transparent to light of asecond color, whereby rays of the second color are sharpened by thefocusing element.
 39. The display system of claim 30, further comprisinga translation assembly selectively moving the focusing element withvibration or rotation.
 40. The display system of claim 39, wherein theretroreflector is coupled to the focusing element whereby thetranslational motion is concurrently applied to the retroreflector bythe translation assembly.
 41. The display system of claim 30, whereinthe focusing element comprises a liquid container, a volume of liquiddisposed in the liquid container, and a perforated sheet disposed in thevolume of liquid to a depth, whereby an array of liquid lenses areformed for focusing the third light.
 42. The display system of claim 30,wherein the angle is 45 degrees.
 43. The display system of claim 29,wherein the display comprises a monitor with a planar display screenarranged parallel to the reflective surface of the retroreflector andwherein the monitor displays the 2D or 3D image at a luminence of atleast 2000 Nits.
 44. The display system of claim 29, further including acontroller and a viewer tracking assembly, wherein the viewer trackingassembly tracks at least one of movement of a viewer or location of theviewer relative to the floating image, and wherein the controllercontrols the display to modify the 2D or 3D image based on processing ofthe tracked movement or location of the viewer.
 45. A display apparatusfor displaying an image that appears to float in a display space,comprising: a display element outputting light associated with an image;a beamsplitter with a first surface receiving the light from the displayelement, wherein the beamsplitter reflects a first portion of the lightand transmits a second portion of the light via a second surfaceopposite the first surface; a first retroreflector with a reflectivesurface facing the display element and the second surface of thebeamsplitter receiving and reflecting the second portion of the lightfrom the display element; and a second retroreflector with a reflectivesurface receiving the first portion of the light reflected from thefirst surface of the beamsplitter and reflecting the first portion backtoward the beamsplitter, wherein the first and second retroreflectorsare oriented in the apparatus whereby the first reflective surface isorthogonal to the second reflective surface, and wherein thebeamsplitter is oriented to place the second surface at a 45 degreeangle to the reflective surface of the first retroreflector.
 46. Thedisplay apparatus of claim 45, wherein the display element comprises amonitor displaying a 2D or 3D image on a display screen at a luminenceof at least 2500 Nits and wherein the display screen is substantiallyplanar and parallel to the reflective surface of the firstretroreflector.
 47. The display apparatus of claim 45, wherein thedisplay element comprises a polarized display and further including anoptical stack disposed between the polarized display and the firstsurface of the beamsplitter, the optical stack including a pair ofquarter wave plates, a half mirror sandwiched between the quarter waveplates, and a reflective polarizer between the first surface of thebeamsplitter and the quarter wave plates.